Change-Id: I489d00bc4ee22a5ecad75dc1eb84776f044566e5
Reviewed-on: https://boringssl-review.googlesource.com/4391
Reviewed-by: David Benjamin <davidben@chromium.org>
Reviewed-by: Adam Langley <agl@google.com>

This extends the packet adaptor protocol to send three commands:
  type command =
    | Packet of []byte
    | Timeout of time.Duration
    | TimeoutAck

When the shim processes a Timeout in BIO_read, it sends TimeoutAck, fails the
BIO_read, returns out of the SSL stack, advances the clock, calls
DTLSv1_handle_timeout, and continues.

If the Go side sends Timeout right between sending handshake flight N and
reading flight N+1, the shim won't read the Timeout until it has sent flight
N+1 (it only processes packet commands in BIO_read), so the TimeoutAck comes
after N+1. Go then drops all packets before the TimeoutAck, thus dropping one
transmit of flight N+1 without having to actually process the packets to
determine the end of the flight. The shim then sees the updated clock, calls
DTLSv1_handle_timeout, and re-sends flight N+1 for Go to process for real.

When dropping packets, Go checks the epoch and increments sequence numbers so
that we can continue to be strict here. This requires tracking the initial
sequence number of the next epoch.

The final Finished message takes an additional special-case to test. DTLS
triggers retransmits on either a timeout or seeing a stale flight. OpenSSL only
implements the former which should be sufficient (and is necessary) EXCEPT for
the final Finished message. If the peer's final Finished message is lost, it
won't be waiting for a message from us, so it won't time out anything. That
retransmit must be triggered on stale message, so we retransmit the Finished
message in Go.

Change-Id: I3ffbdb1de525beb2ee831b304670a3387877634c
Reviewed-on: https://boringssl-review.googlesource.com/3212
Reviewed-by: Adam Langley <agl@google.com>

This regressed in e95d20dcb8. EVP_AEAD will push
errors on the error queue (unlike the EVP_CIPHER codepath which checked
everything internally to ssl/ and didn't bother pushing anything). This meant
that a dropped packet would leave junk in the error queue.

Later, when SSL_read returns <= 0 (EOF or EWOULDBLOCK), the non-empty error
queue check in SSL_get_error kicks in and SSL_read looks to have failed.

BUG=https://code.google.com/p/webrtc/issues/detail?id=4214

Change-Id: I1e5e41c77a3e5b71e9eb0c72294abf0da677f840
Reviewed-on: https://boringssl-review.googlesource.com/2982
Reviewed-by: Adam Langley <agl@google.com>

At the record layer, DTLS maintains a window of seen sequence numbers to detect
replays. Add tests to cover that case. Test both repeated sequence numbers
within the window and sequence numbers past the window's left edge. Also test
receiving sequence numbers far past the window's right edge.

Change-Id: If6a7a24869db37fdd8fb3c4b3521b730e31f8f86
Reviewed-on: https://boringssl-review.googlesource.com/2221
Reviewed-by: Adam Langley <agl@google.com>

Change-Id: I7407261bdb2d788c879f2e67e617a615d9ff8f8b
Reviewed-on: https://boringssl-review.googlesource.com/1505
Reviewed-by: Adam Langley <agl@google.com>